1. Field of the Invention
This invention relates to a process for producing humic acid and other partially oxidized carbonaceous materials via an electrolytic cell. More particularly, the compositions of this invention are prepared by a continuous cyclic technique wherein (a) Fe.sup.+2 ion is oxidized to Fe.sup.+3 in an aqueous acidic electrolyte at the anode of an electrolytic cell with the corresponding production of hydrogen or a metal at the cathode, and (b) the reduction of Fe.sup.+3 generated at the anode with a solid carbonaceous reductant material to Fe.sup.+2 for subsequent reuse in the process.
2. Prior Art
It is well known that carbon and carbonaceous materials may be oxidized at the anode in an electrolyte in an electrochemical cell through which a direct current flows.
Recently, a renewed interest in the electrochemical oxidation of carbonaceous materials has developed wherein coal-assisted generation of hydrogen, or deposition of metals, has been proposed. Thus, U.S. Pat. No. 4,268,363 teaches the electrochemical gasification of carbonaceous materials by anodic oxidation which produces oxides of carbon at the anode and hydrogen or metallic elements at the cathode of an electrolysis cell.
U.S. Pat. No. 4,226,683 teaches the method of producing hydrogen by reacting coal or carbon dust with hot water retained as water by superatmospheric pressure. The pressure is controlled by the use of an inert dielectric liquid which washes the electrodes and while doing so depolarizes them by absorption of the gases.
U.S. Pat. No. 4,233,132 teaches a method wherein the electrodes are immersed within oil which forms a layer over a quantity of water. When current is passed between the electrodes, water is caused to undergo electro-decomposition. Gaseous hydrogen is collected in the sealed space above the oil-water layers, and the oxygen is believed to react with the constituents in the oil layer.
Fray et al., British Patent Application No. 2,087,431 A, disclose that Fe (III) ions generated at the anode of an electrochemical cell may be reduced to Fe (II) ions by contacting the Fe (III) ions with lignite at a temperature greater than 40.degree. C. in a vessel external to the cell.
These represent some of the prior art in attempting to produce useful rates of electrochemically assisted oxidation of carbonaceous fuels. A further example is the use of carbonaceous fuels at the anode of a fuel cell, such devices having failed to achieve commercial realization due to the produces of combustion reducing the efficienty of the system, tars forming on the catalytic surfaces, and the poisoning effect of sulfur and CO.
In view of these problems, it was not thought that the partial electrochemical oxidation of carbonaceous material would selectively produce humic acid, fulmaric acid, carbon black, and other partially oxidized materials. These partially oxidized carbonaceous products find utility in a wide range of industries. For example, among other uses, humic acid is employed as a constitutent in drilling mud.
It has been discovered that these partially oxidized carbonaceous compositions may be prepared by
(a) passing an aqueous acidic electrolyte solution containing iron (II) ions to an electrolytic cell comprising a cathode and an anode;
(b) passing a direct current through said solution, thereby anodically oxidizing at least a portion of said iron (II) ions to iron (III) ions with generation of hydrogen at the cathode;
(c) passing said hydrogen and said iron (III) ions from the cell;
(d) reducing the iron (III) ion oxidation product in the aqueous acidic electrolyte to iron (II) ions by contacting the same with a solid carbonaceous reducing agent at a temperature in the range of from 100.degree. C. to 200.degree. C.; and
(e) recycling at least a portion of the aqueous acidic electrolyte containing the iron (II) ions from step (d) to step (a) until sufficient current has been passed through the cell to elevate the oxygen level of the carbonaceous material to between 10% and 40%.
U.S. Pat. No. 4,202,744 teaches a method wherein elemental iron is oxidized in an aqueous solution of an alkali metal hydroxide at the anode of an electrolytic cell with simultaneous generation of hydrogen at the cathode. The iron oxidation products of the reaction are thereafter reduced to elemental iron by contact with a carbonaceous reducing agent at elevated temperatures and the reduced material recycled for reoxidation. Carbon monoxide is the preferred reducing agent and temperatures above 1000.degree. F. are recommended.